Scientists using an electrically charged needle have electrospun nanosize threads of cells encased in plastic polymers to create living microfibers that promote tissue regrowth. Unfortunately, the electrical charge can hurt both the spun cells and the scientists doing the spinning. But now mechanical engineers Suwan Jayasinghe and Sumathy Arumuganathar of University College London have invented a way to spin nanothreads using only pressure and, with the help of medical colleagues, shown that they can create such nanothreads of living heart tissue, potentially revealing the way to weave an entirely new, healthy heart or even fresh, new skin.

"[We can] remove the electric field and use pressure to draw the fibers," Jayasinghe says. "You can make scaffolds with living cells with this technique as well, which shows that this technique can be used right across the board."

The researchers successfully used this method to spin tissue from smooth muscle cells from rabbit aortas with a special device comprising three concentric needles: an inner needle pushing out the cells, a second needle ejecting an encasing polymer, and a third, surrounding needle that applies pressure. By flowing the cells at a slow rate, the polymer at a slightly faster rate, and applying pressure (ranging from slightly less to nearly double that of the atmosphere), Jayasinghe and his colleagues teased out a microthin, continuous thread. "Some of the simplest things in life are some of the things that are unexplored," Jayasinghe says. "Increase the pressure and you get thinner fibers."

Cells that were subjected to such pressures showed no immediate ill effects nor any three weeks later compared with untreated controls, according to a paper outlining the findings online in Biomedical Materials. The technique may allow researchers to create living scaffolds of cells to deliver drugs as well as grow or regenerate the heart and other organs.

But unlike electrospinning, the new method does not currently allow researchers to easily align living cells, Jayasinghe notes. The natural concentrations of charged molecules in such cells line them up when exposed to an electrical charge, as long as the cells are evenly spaced. In contrast, the pressure technique tends to deliver cells in clusters but researchers say the problem may be solved by smoothing out the spacing of the cell mixture.

Regardless, the novel technique will allow engineers to play with new types of materials, such as metal nanoparticles that would have disrupted an electrical charge. "You can directly thread very highly conducting composite materials to polymers that were previously unexplored," Jayasinghe says.

The team is now testing the gene production of the resultant cellular nanothreads to determine their safety. "You wouldn't want to put cancerous cells back into anybody's body," Jayasinghe notes. He adds that researchers are also exploring the potential of spinning such nanothreads from stem cells. "Stem cells will differentiate into anything," he says. "They can go on your heart or on your skin, they can go anywhere."

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